7.7
Function Composition Syntax
This library provides an alternative #%app syntax that interprets double dots as (unary) function composition. The syntax is lightweight and extensible through syntax parameters, allowing alternative base forms of #%app to be substituted. Included with this package is integration with the fancy-app module, to make composition of anonymous functions as painless as possible.
Source code for this library is avaible at https://github.com/jackfirth/compose-app
1 API Reference
| (require compose-app) | package: compose-app |
syntax
(compose-app func-expr dotted-func-expr ...)
func-expr = single-expr | many-expr ... dotted-func-expr = .. func-expr
Expands into a function composition of each func-expr, with function
application for the expanded composition defined in terms of
compose-app-base-app. If a func-expr is a single-expr,
the expression is used directly, but in the many-expr case the
expression used for that function is
(compose-app-group many-expr ...). The compose-app
module additionally provides compose-app as #%app. If no uses
of .. are found, an expansion to a normal function application (still
in terms of compose-app) is used.
Examples:
> ((add1 .. string->number .. first) '("15" "2" "96")) 16
> (define ((mapped f) vs) (map f vs)) > ((rest .. (mapped string->symbol) .. string-split) "foo bar baz") '(bar baz)
> ((rest .. mapped string->symbol .. string-split) "foo bar baz") '(bar baz)
The composition produced by compose-app is a single-argument function defined in terms of compose-app-base-lambda, which defaults to lambda from racket/base.
syntax
A syntactic element used by compose-app. Usage anywhere else is a
syntax error.
syntax
A syntax parameter that defines how compose-app treats multiple
expressions in the same function segment. Defaults to
compose-app-base-app.
syntax
A syntax parameter that defines what function application syntax
compose-app expands to. Defaults to #%app from
racket/base. Changing this allows compose-app to be
used with other libraries providing modified versions of #%app.
syntax
A syntax parameter that defines what anonymous function syntax
compose-app expands to. Defaults to lambda from
racket/base. This parameter should always be a macro
that accepts expressions like lambda does, but it will only
ever be used to produce single-argument functions. Changing this
allows compose-app with other definitions of anonymous
function semantics.
2 Integration with fancy-app
| (require compose-app/fancy-app) | package: compose-app |
syntax
Example:
> ((map string->number _ .. rest .. string-split) "1 10 100") '(10 100)